The present invention relates to video signal processing circuits, and more particularly, to a digital video signal processing circuit which outputs a static image with little image deterioration in a magnetic recording and reproducing apparatus to record and reproduce video signals in composite digital signal form.
In a magnetic recording and reproducing apparatus (video tape recorder, hereinafter referred to as "VTR"), not only reproduction of recorded video signals at ordinary speed but also the function of special reproduction such as static image reproduction or slow motion reproduction are required.
In such video devices for adopting color television system of NTSC, it is preferable always to satisfy the provisional standard RS-170A (present standard of NTSC system) of the EIA (Electronic Inductry Association). For example, when such a video device records video signal in composite signal form and a field static image is outputted, video signal processing is necessary which produces and outputs an image of four sheets of fields corresponding to the NTSC television system from an image of one sheet of a field by the so-called chroma invert technology of reading the record signal and inverting only the chrominance signal among a luminance signal (Y signal) and a chrominance signal (C signal). Such chroma invert technology is disclosed, for example, in U.S. Pat. No. 4,528,598.
In the prior art as above described, when the chrominance signal in a chroma invert circuit is inverted, the phase of the luminance signal with a frequency in the vicinity of color subcarrier (f.sub.sc =3.58 MHz) is also inverted.
Consequently, at the chroma invert state, the wave form of a luminance signal is not held due to the phase inversion of a high region component among the luminance signal, and deterioration of the horizontal resolving power of the reproduction image or deterioration of the edge portion is generated.
When image corresponding to two continuous fields recorded in the signal processing circuit is inputted and a so-called frame static image is outputted, flicker is produced at the motion portion of the image and the picture quality is deteriorated.